Former JetBlue flight attendant Steven Slatershowed up in court this morning in NYC and will voluntarily admit himself into a mental health program for treatment, if the D.A. plea bargains his criminal case and agrees to a lesser sentence.

Steven -- who faces 7 years in prison for charges including reckless endangerment -- claimed a passenger went off on him and hit him on the head with the overhead bin, however sources at JetBlue tell TMZ there is no evidence this ever happened -- i.e., Slater made it up.

The D.A. and Slater's lawyer, Daniel Horwitz, agreed to meet and try and hash out the deal before the next court hearing.

TMZ was in court and heard Horwitz and the D.A. discussing a plea bargain and a mental health program near the judge's bench -- in front of the judge.